The UK's biggest testing lab has been hit by an outbreak of coronavirus after what one worker claimed were repeated breaches of COVID safety rules, Sky News has learned.
Positive cases have been reported in three of the four scientific teams at the Milton Keynes Lighthouse Laboratory, as well as among administrative and warehouse staff at the site.
It is not known how many people have been affected by the outbreak, but around 20 people in one 70-person lab team are currently isolating, according to a worker at the laboratory who asked to remain anonymous.
The outbreak has placed considerable strain on the lab, which has been asked to process 70,000 tests a day in order to keep up with rising demand.
The source said that 47,000 were processed on Tuesday, adding: "No chance we'll ever hit 70,000 a day the way we're going."
The lab worker also raised concerns about the safety of the lab, saying that rules put in place to keep staff safe were being broken in order to meet targets - a claim the Department of Health and Social Care denied.
Sky News understands the Lighthouse Lab is supposed to have a bubble system in place in order to keep staff separate, following a recommendation from the Health and Safety Executive, which visited the site recently.
Yet according to the source, the bubble system is not being respected with workers at the short-staffed lab being moved between groups, risking further cross-contamination.
The lab worker said there had also been mixing in the building's lobbies and at the canteen.
Staff at the laboratory have been offered an unlimited number of tests and new staff are tested when they arrive.
The lab worker said that new recruits had been sitting in the canteen while they waited for their test results.
According to the lab worker, one new warehouse staff member received a positive test result after they had sat in the canteen during a period when a whole lab team had been in there for a break.
"The whole thing's a joke," they said.
Staff at the Lighthouse Labs have given up Christmas in order to work 12-hour shifts in what the source described as "cramped working conditions" at the Milton Keynes laboratory, which is based at the UK Biocentre.
The centre was converted in April into the largest testing lab in the UK, capable of processing tens of thousands of tests a day.
The Lighthouse Lab system has dramatically increased the UK's testing capacity but has been criticised for not being sufficiently connected to the rest of the healthcare service.
Sky News understands the administration is still largely run by a team from management consultancy Deloitte.
A spokesperson for the Department of Health and Social Care confirmed it was aware of the outbreak at the Lighthouse Laboratory, but insisted all government guidelines on COVID-secure work procedures had been followed.
"NHS Test and Trace continues to test record numbers of people and people can have confidence that if they have symptoms and need a test, they can get one," they said.
"We are delivering an unprecedented volume of tests - more than 450,000 yesterday alone - and during periods of high demand our focus is ensuring that anyone with symptoms can get a test.
"All our test sites and our home test service will be available for bookings as normal over the Christmas period."